Month: September 2008

My bitx project has been lying dormant for a couple of months now. I completed wiring about 2 months back. The transmitter was working properly. But the receiver was not receiving anything . When I tried to increase volume, it started howling. After initial testing, I became QRL with lot of other activities. This weekend I decided to look at bitx board again. I carefully rechecked all stages and found out that I had made 2 mistakes in wiring components , a 22 ohms resistor was in the place of 220 ohm and at another place I put a 1k instead of 100 ohm. After correcting the mistakes I fired up the receiver , I could hear some CW transmission around 14.01Mhz. When I increased the volume, the audio stage was howling. I decided to discard the audio stage and build a new one. I bought a small audio module form local market for Rs 25 and fixed it to the board. Now the audio is clean even when the volume is maximum. I am still not satisfied with the sensitivity of the receiver. I made the following measurements on various transistors today. The table of the voltages on transistors are given below. The transistors numbers are based on Bitx V3 diagram by OM vu2wmj Rahul.

We run our college lab on LTSP built on Debian Etch. Today, one of our students inadvertently ran a fork bomb and the entire lab was stuck. We had to reboot the system. On examining the code , it was found that he put fork system call in an infinite loop.

A fork bomb is a process that ‘explodes’ by recursively spawning copies of itself. It will eventually eat up all your computing resources .

On Linux systems you can set the maximum number of processes that a user can run.

You can explore your current limits via the ulimit command. This is what I got on my debian etch installation at home.

There are soft limits and hard limits. Soft limits are default values. However hard limits are enforced via kernel. So a user can change his soft limit up to the hard limit using the ulimit command. For details ,RTFM ulimit.

This wikipedia article is very informative and a must read for all sysadmins. There are lot of example bombs you can try :D.

Pardus Kurulan 2008 is a cool Linux distribution from Turkey. It differs from conventional Linux distributions in several ways. This was pointed out to me by Sarath. Last night I installed Pardus on a Virtual Box virtual machine to explore this distro. I will share some of the screen shots and observations that I made in the process.

Installation

The minimum hardware requirement for installation of pardus 2008

256 MB memory (512 MB recommended)

800 MHz Intel or AMD processor (1200 MHz recommended)

At least 4 GB of free hard disk space (10 GB recommended)

The opening screen for installer is like any other distro. The default screen is is Turkish. Press F3 and select English. Select boot from CD. The following screen will come up with a copyright notice.

Copyright Screen

Once you press agree and then next, it proceeds to ask you the time zone and default user name. I could not locate the Indian time zone on the screen. See the screen shot below.

Time zone Selection

You can assign administrative privileges to user. To quote the release notes, the privileges of all users may be arranged and the password inquiry behavior may easily be customized by using the advanced user authorization system of Pardus 2008. I am yet to try it out.

User name selection

Next, you can select the partition to which Pardus should be installed. The screen shot below shows the screen.

Partition Selection

The installation then proceeds smoothly. Finally you will be asked to install the boot loader. I selected master boot record ( I am on a virtual machine). The default boot loader is grub. Then the machine rebooted . I got the following screens .

Login Screen

Pardus running.

Exploring Pardus

The first thing I noticed about Pardus is the installer. The installer is named YALI ( Yet another Linux installer). YALI is smooth and intuitive. Secondly I was surprised to see how fast the Pardus booted up on my VirtualBox virtual machine( Of course I have a Pentium 2 Quad processor and plenty of memory). Upon digging further , I found that all the startup scripts have been rewritten in python. All the conventional startup code have been removed and replaced with clean python code. No wonder the startup time is very low. The startup script in Pardus is called mudur. If you are looking for further info on this you can read this paper on mudur. I am yet to learn the startup process fully.

Pardus uses a modified version of KDE 4 as the default desktop. It is called Kaptan . Another interesting feature is that the package management system is also re written. It is called pisi. Of course you can use pisi on command like like apt or via a graphical user interface.

PiSi (Packages installed Successfully)

The Pardus configuration utility is called TASMA. It is very user friendly and I could configure all my devices quickly.

TASMA

Pardus has several other features.Take a look at this page to find out . This distro looks fresh and interesting. Hopefully we will see some of these cool programs ported to other mainstream distros very soon.

The national program of technology enhanced learning (NPTEL) is an initiative of the Government of India to provide quality educational material to engineering students . The site has several video tutorials for various engineering subjects. However, the site is not very popular among Indian students. I have been trying to promote it among my students and colleagues for quite some time as a source of quality material. But, the response is not very encouraging.

The videos are hosted on youtube. The complete playlist is here. There are several course suitable for electronics /computer science students. Some of the so called “difficult” subjects are lucidly explained by senior professors. I have recomended the digital signal processing course by Prof. S C Dutta Roy as supplimentary material to my students.

If you want to view the courses offline, you can download it form youtube using youtube-dl. The youtube videos are in flash (.flv) format. Softwares such as ffpeg can be used to convert them to your favorite format.

My kids are having holidays for next 10 days in connection with Onam. During holidays, I let them play Gcompris if i am not using the computer. Today they wanted to play. I instead of letting them play Gcompris , I showed them StoryTellng Alice They were hooked to it within half an hour. By evening they showed me a small animation they built. I am pretty amazed at the pace at which my daughters ( aged 8 and 7) learn.

Story telling Alice is a spin of from Alice , a great programming environment for teaching programming to kids. Alice is the brain child of Randy Pausch.